I built a medic not too long ago (not posted) much like this, all I have to say is the cab is a little to long.

i hope you can make a little money! for about $20 you could buy a camper,and make an ambulance like i did! i hope you change your mind about a 4 stud front,because i think it does nt look scale convincing enough! are you ambitious enough to attempt 5 stud front? or maybe 6 stud front and 7 stud cargo rear? if so,know that this has never been achieved by anyone to my knowlege! but i guess that it would be the best looking and realistic ambulance in the world for this scale, something to strive for! unfortunately, it would also mean the costliest! good luck for your project!